New find sheds light on Earth’s largest me­te­orite field

China Daily (USA) - - XINJIANG - ByXINHUA in Nan­jing

Chi­nese sci­en­tists have for­mally an­nounced the dis­cov­ery of Earth’s long­est me­te­orite strewn field in Al­tay, the Xin­jiang Uygur au­tonomous re­gion.

Ex­perts from the Pur­ple Moun­tain Ob­ser­va­tory in Nan­jing, Jiangsu prov­ince, made the an­nounce­ment on Oct 13 af­ter study­ing the chem­i­cal com­po­si­tion of three me­te­orites and dis­cov­er­ing that they were all from the same par­ent as­ter­oid.

The ear­li­est known dis­cov­ery of ex­trater­res­trial stones in the field was in 1898, when herds­men in the Gobi Desert found a sil­very camel-shaped stone weigh­ing 28 met­ric tons.

The Me­te­oritic So­ci­ety later named it Ar­manty, and con­firmed it to be the world’s fourth-largest me­te­orite.

More than 100 years later, a sec­ond one was found. It weighed 430 kg and was named Ul­a­sitai.

But it was not un­til 2011, when the 5-met­ric-ton Wux­i­like was un­cov­ered, that sci­en­tists be­gan to no­tice that the three me­te­orite were in a line that stretched across 425 km.

“They are on the same axis from south­east to north­west, which piqued our in­ter­est,” said Xu Weib­iao, me­te­orite cu­ra­tor with the ob­ser­va­tory un­der the Chi­nese Academy of Sci­ences.

Tests re­vealed that all three me­te­orites were com­posed of the same chem­i­cal com­po­nents and mi­croele­ments, as were sev­eral smaller rock­ers found in the field.

Xu Weib­iao,

me­te­orite cu­ra­tor, Chi­nese Academy of Sci­ences

“This sug­gests that the me­te­orites were all from the same par­ent as­ter­oid be­fore it sep­a­rated as it en­tered the Earth’s at­mos­phere,” Xu said.

An or­di­nary me­teor shower can scat­ter me­te­orites across dozens of kilo­me­ters.

Be­fore the find­ing in Al­tay, the world’s largest me­te­orite strewn field was Gibeon, with a long axis of 275 km.

Judg­ing by the 425-km strewn length of the Al­tay field, its me­teor shower was likely the largest on the Earth.

How­ever, there is no his­tor­i­cal doc­u­men­ta­tion on the in­ci­dent, so sci­en­tists spec­u­late it might have hap­pened pre­his­tor­i­cally.

“A me­teor shower of such a scale must have had a great im­pact on the Earth,” Xu said. “If it hap­pened af­ter hu­mans walked the earth, we of­ten find cave paint­ing de­pict­ing the in­ci­dent in the area.”

He said the team had used iso­topic dating to de­ter­mine when the me­teor shower oc­curred.

An av­er­age of 20,000 me­te­orites fall to the Earth ev­ery year, which sci­en­tists use to de­ter­mine in­for­ma­tion about the uni­verse.

For ex­am­ple, ev­i­dence of vol­canic ac­tiv­ity on Mars 200 mil­lion years ago was dis­cov­ered by sam­pling a me­te­orite.

In 2017, China will launch the Chang’e-5 lu­nar probe, which will col­lect rock sam­ples from the moon.

“For the moon sam­ple re­search, the ob­ser­va­tory will use more ad­vanced an­a­lyt­i­cal equip­ment, which will greatly as­sist our petro­log­i­cal and min­er­alog­i­cal re­search,” Xu said.

A me­teor shower of such a scale must have had a great im­pact on the Earth.”

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